1. Field of the Invention
The present invention relates to a communication terminal device or system such as a facsimile or teletex machine.
2. Related Background Art
In a prior art facsimile machine, when data sent through a line is to be received, it is temporarily stored in a RAM (random access memory) and a printer prints out the data on a record paper in accordance with the data stored in the RAM. When data is to be transmitted, a text is read by a reader the read data is temporarily stored in the RAM, and a signal is sent to the line in accordance with the data stored in the RAM. In the receiving and transmitting operations, the data is compressed and decompressed.
Since the RAM has the shortcoming that the memory content is destroyed when the power supply is turned off, use of a non-volatile memory such as a hard disk instead of the RAM has been proposed.
In this case, if there is an error between the non-volatile memory and a communication control unit (CCU) during the receiving operation, the data is not correctly stored in the non-volatile memory even if the data is correctly received. As a result, the received text cannot be correctly printed out. A sending station may not know when such an error occurs. In this case, the reliability of the received text is lowered. From the viewpoint of the sending station, it leads to reduction of reliability of transmitting text.
The facsimile machine is classified into class 1 machines, which can send and receive only image data, class 2 machines, which can send and receive image data and can only receive character code data, and class 3 machines, which can send and receive image data and character code data. The class 3 machine can efficiently transmit a document in which character code data and image data are mixedly contained.
The class 3 machine (mixed mode terminal) cannot send character code data to a class 1 machine. Further, the mixed mode terminal cannot send image data to a teletex machine.
It may be possible to connect a display means such as a CRT to the facsimile machine to display the received image data on the CRT. It may also be possible to edit images and characters to be sent on the CRT. If data is receiving during the editing, an indicator such as a lamp may be turned on to notify the operator of the reception of the data.
In this case, the indicator is required separately from the CRT and the number of parts required increases.
When the non-volatile memory is connected to the communication terminal device, all power supplies are kept on in order to allow automatic reception. This wastes power. Further, since the hard disk is rotated for a long time, the lifetime of the hard disk is shortened. In order to overcome the above shortcomings, the power supply of the terminal may be kept off until data is received, when the power supply is turned off. In this case, however, a certain time is required before the facsimile machine starts, and the line has to wait for the start-up.
Where a reader of one station is of high resolution and a printer of another station is of low resolution, a long transmission time is needed if the high density data read by the reader is transmitted as it is and the other station converts the density of the received data.